Architecture & Structures

8/19/2019 Architecture & Structures

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ARCHITECTURE &

STRUCTURESLecture 6 – An overview of Bridges


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ARCHITECTURE & STRUCTURE AN OVERVIEW OF BRIDGES

Introduction

Bridges are structures that are constructed to

transport people from on point to another across

a river or an intersection of roads .

Types of Bridges:

Beam Bridges

Truss Bridges Arch Bridges

Suspension Bridges

Cable-Stayed Bridges


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ARCHITECTURE & STRUCTURE AN OVERVIEW OF BRIDGES

History of Bridges

The Chinese constructed the first bridge as simple

suspension structure using bamboo. During the

post war years the bridges were constructed in

stone masonry and timber using “arch” principle.

Architect/Engineer – Santiago Calatrava is known

for his amazingly sculptural bridges designed by

applying structural principles derived form the

study of natural structures.


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ARCHITECTURE & STRUCTUREBEAM TYPE BRIDGES

Beam – is abridge whose load-bearing

superstructure is composed of a beam.

The beam type is the simplest type of bridge.

It is made of two or more supports which hold up abeam.

http://library.thinkquest.org/J002223/types/beam.htmlhttp://en.wikipedia.org/wiki/Bridgehttp://en.wikipedia.org/wiki/Superstructurehttp://en.wikipedia.org/wiki/Superstructurehttp://en.wikipedia.org/wiki/Bridgehttp://library.thinkquest.org/J002223/types/beam.html


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ARCHITECTURE & STRUCTURETRUSS TYPE BRIDGES

Truss bridge is abridge whose load-bearing

superstructure is composed of atruss.

Truss is a structure with several elements

connected together forming triangular units. Theconnected elements (typically straight) may be

stressed fromtension,compression, or

sometimes both in response to dynamic loads.

Truss bridges are one of the oldest types ofmodern bridges.

A truss bridge is economical to construct because

its uses materials efficiently.

http://en.wikipedia.org/wiki/Bridgehttp://en.wikipedia.org/wiki/Superstructurehttp://en.wikipedia.org/wiki/Trusseshttp://en.wikipedia.org/wiki/Tension_(mechanics)http://en.wikipedia.org/wiki/Compression_(physical)http://en.wikipedia.org/wiki/Compression_(physical)http://en.wikipedia.org/wiki/Tension_(mechanics)http://en.wikipedia.org/wiki/Trusseshttp://en.wikipedia.org/wiki/Superstructurehttp://en.wikipedia.org/wiki/Bridge


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ARCHITECTURE & STRUCTURE ARCH BRIDGES

Anarch bridge is a bridge withabutments at

each end shaped as a curvedarch.

Arch bridges work by transferring the weight of

the bridge and its loads partially into ahorizontal thrust restrained by the abutments at

either side.

Aviaduct (a long bridge) may be made from a

series of arches,The roadway is located on top of the arch.

http://en.wikipedia.org/wiki/Abutmenthttp://en.wikipedia.org/wiki/Archhttp://en.wikipedia.org/wiki/Structural_loadhttp://en.wikipedia.org/wiki/Viaducthttp://en.wikipedia.org/wiki/Viaducthttp://en.wikipedia.org/wiki/Structural_loadhttp://en.wikipedia.org/wiki/Archhttp://en.wikipedia.org/wiki/Abutment


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ARCHITECTURE & STRUCTURE ARCH BRIDGES

The Alcántara Bridge, Spain (built 103-106 AD)

http://en.wikipedia.org/wiki/Alc%C3%A1ntara_Bridgehttp://en.wikipedia.org/wiki/Alc%C3%A1ntara_Bridgehttp://en.wikipedia.org/wiki/Alc%C3%A1ntara_Bridgehttp://en.wikipedia.org/wiki/Alc%C3%A1ntara_Bridge


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ARCHITECTURE & STRUCTURES VIADUCT


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ARCHITECTURE & STRUCTURESUSPENSION BRIDGES

Asuspension bridge is a type ofbridge in

which the deck (the load-bearing portion) is hung

below suspensioncables on vertical suspenders.

This type of bridge has cables suspended

betweentowers, plus vertical suspender

cables that carry the weight of the deck below,

upon which traffic crosses. This arrangementallows the deck to be level or to arc upward for

additional clearance.

http://en.wikipedia.org/wiki/Bridgehttp://en.wikipedia.org/wiki/Wire_ropehttp://en.wikipedia.org/wiki/Towerhttp://en.wikipedia.org/wiki/Towerhttp://en.wikipedia.org/wiki/Wire_ropehttp://en.wikipedia.org/wiki/Bridge


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TheGolden Gate Bridge in San Francisco

http://en.wikipedia.org/wiki/Golden_Gate_Bridgehttp://en.wikipedia.org/wiki/Golden_Gate_Bridge


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Akashi Kaikyō Bridge


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Advantages

A suspension bridge can be made out of simple materials

such as wood and common wire rope.

Longer main spans are achievable than with any other

type of bridgeLess material may be required than other bridge types,

larger spans can also be achieved, leading to a reduced

construction cost

Except for installation of the initial temporary cables,

little or no access from below is required duringconstruction, for example allowing a waterway to remain

open while the bridge is built above

May be better to withstand earthquake movements than

heavier and more rigid bridges


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Disadvantages

Considerable stiffness or aerodynamic profiling

may be required to prevent the bridge deck

vibrating under high winds.

The relatively low deck stiffness compared to

other (non-suspension) types of bridges makes it

more difficult to carryheavy rail traffic where

high concentrated live loads occur

Some access below may be required during

construction, to lift the initial cables or to lift

deck units. This access can often be avoided in

cable-stayed bridge construction

http://en.wikipedia.org/wiki/Passenger_rail_terminologyhttp://en.wikipedia.org/wiki/Cable-stayed_bridgehttp://en.wikipedia.org/wiki/Cable-stayed_bridgehttp://en.wikipedia.org/wiki/Passenger_rail_terminology


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ARCHITECTURE & STRUCTURECABLE-STAYED BRIDGES

Acable-stayedbridge has one or

moretowers (or pylons), from whichcables

support the bridge deck.

Abdoun Bridge, Amman,Jordan

http://en.wikipedia.org/wiki/Bridgehttp://en.wikipedia.org/wiki/Wire_ropehttp://en.wikipedia.org/wiki/Abdoun_Bridgehttp://en.wikipedia.org/wiki/Abdoun_Bridgehttp://en.wikipedia.org/wiki/Ammanhttp://en.wikipedia.org/wiki/Jordanhttp://en.wikipedia.org/wiki/Jordanhttp://en.wikipedia.org/wiki/Ammanhttp://en.wikipedia.org/wiki/Abdoun_Bridgehttp://en.wikipedia.org/wiki/Abdoun_Bridgehttp://en.wikipedia.org/wiki/Wire_ropehttp://en.wikipedia.org/wiki/Bridge


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There are two major classes of cable-stayed

bridges:

1)harp

2) fan.

In theharp or parallel design, the cables are

nearly parallel so that the height of their

attachment to the tower is proportional to thedistance from the tower to their mounting on the

deck.


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In the fan design, the cables all connect to or pass

over the top of the towers.

The fan design is structurally superior with

minimum moment applied to the towers but for

practical reasons the modified fan is preferred

especially where many cables are necessary.

In the modified fan arrangement the cables

terminate near to the top of the tower but are

spaced from each other sufficiently to allow bettertermination, improved environmental protection,

and good access to individual cables for

maintenance.


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The cable-stayed bridge is optimal for spans

longer thancantilever bridges, and shorter than

suspension bridges.

This is the range where cantilever bridges wouldrapidly grow heavier if the span were lengthened,

and suspension bridge cabling would not be more

economical if the span were shortened.

http://en.wikipedia.org/wiki/Cantilever_bridgehttp://en.wikipedia.org/wiki/Suspension_bridgehttp://en.wikipedia.org/wiki/Suspension_bridgehttp://en.wikipedia.org/wiki/Cantilever_bridge


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ARCHITECTURE & STRUCTURECOMPARISON BETWEEN SUSPENSION BRIDGE AND CABLE

STAYED BRIDGE

Cable-stayed bridges may appear to be similar to

suspension bridges, but in fact they are quite different in principle

and in their construction.

In suspension bridges, large main cables (normally 2) hang between

the towers (normally 2), and areanchored at each end to the

ground.This can be difficult to implement when ground conditions are poor.

The main cables, which are free to move on bearings in the towers,

bear the load of the bridge deck. Before the deck is installed, the

cables are undertension from their own weight. Along the main

cables smaller cables or rods connect to the bridge deck, which islifted in sections.

As this is done, the tension in the cables increases, as it does with

thelive load of traffic crossing the bridge. The tension on the main

cables is transferred to the ground at the anchorages and by

downwards tug on the towers.

http://en.wikipedia.org/wiki/Suspension_bridgehttp://en.wikipedia.org/wiki/Earth_anchorhttp://en.wikipedia.org/wiki/Tension_(mechanics)http://en.wikipedia.org/wiki/Live_loadhttp://en.wikipedia.org/wiki/Live_loadhttp://en.wikipedia.org/wiki/Tension_(mechanics)http://en.wikipedia.org/wiki/Earth_anchorhttp://en.wikipedia.org/wiki/Suspension_bridge


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STAYED BRIDGE

Difference between types of bridges

Suspension bridge

Cable-stayed bridge,

fan design harp design


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STAYED BRIDGE

In the cable-stayed bridge, the towers are the primary load-

bearing structures which transmit the bridge loads to the

ground.

A cantilever approach is often used to support the bridge deck

near the towers, but lengths further from them are supported

by cables running directly to the towers.This has the disadvantage, compared to the suspension bridge,

that the cables pull to the sides as opposed to directly up,

requiring the bridge deck to be stronger to resist the resulting

horizontalcompression loads; but has the advantage of not

requiring firm anchorages to resist the horizontal pull of themain cables of the suspension bridge.

By design all static horizontal forces of the cable-stayed bridge

are balanced so that the supporting towers do not tend to tilt or

slide, needs only to resist horizontal forces from the live loads.

http://en.wikipedia.org/wiki/Compression_(physical)http://en.wikipedia.org/wiki/Compression_(physical)


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STAYED BRIDGE


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STAYED BRIDGE

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